Ubiquiti AirOS Firewall Configuration Example:
This example assumes your Ubiquiti Router is configured in SOHO Router Mode and that this router is also performing NAT. This can be achieved by starting with a Ubiquiti AirOS Router (i.e. AirRouter or PowerAPN) that is using the factory default settings.
Configure Port Forwarding:

This scenario is based on using a DrayTek ADSL Modem configured in bridge mode which passes the pppoe connection directly to the PowerAPN or MikroTik Router. If you are using a standard ADSL modem (Telecom/Vodafone/D-Link etc) you will need to configure your firewall rules on the Modem and again on the PowerAPN (i would change the PowerAPN to bridge mode instead of its current Router mode so the Modem is the only firewall that traffic traverses on your network as configuring port forwarding through multiple Firewalls (Double NATing) is difficult and messy.